This invention relates to cooling jet apparatus which use a mixture of liquid and gas for cooling or quenching. More particularly, it relates to misting cooling jet nozzles which are operable at relatively low gas pressure while providing relatively high cooling capacity.
In the manufacturing and processing of many types of products, it may be necessary to subject the workpiece to heating and cooling processes, particularly in continuous operations. Cooling may be accomplished in numerous ways, including providing a cooling or quenching fluid jet which is applied to the workpiece surface. The cooling or quenching jet may involve the use of gases, liquids, or mixtures of gases and liquids. Air and inert gases are commonly used gases and water and oils are commonly used liquids for use in cooling or quenching jets. As used herein, all references to "air" include and mean any and all suitable gases, generally, and all references to "water" include and mean any and all suitable liquids, generally.
In various metallurgical applications, such as at the exit end of an annealing furnace or in continuous metal-casting operations, it is necessary to produce a cooling or quenching jet which is applied to the surface of an alloy workpiece. Cooling or quenching in these applications may involve the application of air or water, and where more drastic cooling action is required, it is known to employ mist cooling. Mist cooling involves the use of air under high pressure to form a mist by ejecting water at high speed from a nozzle with air. The cooling capacity of the resulting mist jet is determined by the momentum of the jet and the air/water ratio of the mist comprising the jet. In conventional misting jet systems, most of the energy of the pressurized air is consumed in forming the mist with only the remaining energy being used to produce the mist jet impact. Typically, conventional nozzle designs provide for air and water to enter the nozzle mixing chamber at near right angles such that the air must move and accelerate the water from a zero or low velocity to a discharge velocity in the direction of the jet.
As used herein, all references to "pressures" include and mean differential pressures, unless otherwise stated.
What is needed is a misting jet nozzle which is operable at relatively low air pressures, on the order of less than 10 psi (68.95 kPa), while providing a relatively high cooling capacity. It is a primary object of the present invention to provide such a misting jet nozzle. The nozzle should also provide varying and different cooling rates, as may be required, by regulating primarily the water pressure. It is also desirable to provide a nozzle having a design which facilitates formation of water droplets for mist cooling.